Spec tests are breaking upon @modelcontextprotocol/modelcontextprotocol merging a PR into main

[KKonstantinov]

Describe the bug
Our spec.test.ts is currently running against the main branch of the https://github.com/modelcontextprotocol/modelcontextprotocol repo.

Any merge that affects spec types on the main repo will go on and break the test on the TS SDK repo.

To Reproduce
Steps to reproduce the behavior:

1. Merge any breaking change to https://github.com/modelcontextprotocol/modelcontextprotocol/blob/main/schema/draft/schema.ts
2. Test will break in the TS SDK immediately, if there isn't a timed PR merge here as well

Expected behavior
TS SDK shouldn't break when an exterior dependency (in this case, quite an important one...) is changed.

Additional context

• Solution would be to add one set of checks which fail if spec isn't matching - and bind that to a tag in the https://github.com/modelcontextprotocol/modelcontextprotocol repo, e.g. https://github.com/modelcontextprotocol/modelcontextprotocol/blob/2025-06-18/schema/draft/schema.ts
• Then an additional set of tests which compare to the main branch but are not failing in nature, but could just issue warnings or similar.